PLATE V. 



(Miiller). 



1. a, b. Posterior and dorsal view of a pair from the Regent's 



Canal, N.W. London. 



2. a, 6. of a pair from the Thames at Hampton Wick. 



Middlesex. 



3. , 6. 'of a pair from the Holton Canal, Lancashire. 



4. a, ft. of a pair } from the Pleistocene at Crayford- 



4. c, d. of a right valve j Erith, Kent. 



5. , ft. of a pair from the Cromerian at West Runton, 



Nbrfblk-. 



6. a, 6. of a pair from the Pleistocene at .Barn well Abbey, 



Cambridgeshire. 



7. a, ft. of left Valve of " var. danubialit" from the Pleisto- 



cene at Crayford-Erith, Kent. 



8. a, ft. of right valve of the same from the Pleistocene at 



Grays, Essex. 



9. a, ft. - of & left valve of a strongly striate example from 



the Pleistocene at Grays, Essex. (P. stdcutum, 

 pars, of S, P. Woodward's coll.) 



11. a-f. External left aspect of a series of different ages from the 



Thames at Hampton Wick, Middlesex. 



12. a-cL of young shells from Newton Abbott, Devon. 



13. External right aspect of adult shell from the Regent's 



Canal, tf.W. London. 



14. External left aspect of adult shell from the Eolton Canal. 



Lancashire. 



15. External right aspect of adult shell from the Thames at 



Hampton Wick, Middlesex. 



16. from the Spandauer Canal, Berlin. ("Var. 'lo;fnta.") 



17. a-f?. External right aspect of a series of different ages of 



' var. nova, Paul.^', from St. Canxian, Croatia. 



18. - of adult shell from tire Coin at West Drayton. 



Middlesex: 



S, Sandberger. 



10. , ft. Posterior arid dorsal View of a left Valve from tho 

 Pleistocene at Grays, Essex. ( f\ mtlctihuii; pars, of 

 S. P. Woodward's coll.) 



*** Thf> softie in millimetrts under ea'ch RghVe, or sprigs 'of fip-uros, 

 fckows tTif am'oulU 



